1. Field of the Invention
The invention relates to the field of machines for renal replacement therapy.
2. Description of the Related Art
In hemodialysis, blood is removed continuously from a patient in an extracorporeal circulation, passed through a hemodialyzer and reinfused back into the patient. In doing so, a mass exchange is performed, very similar to that taking place in the kidneys. The hemodialyzer consists of two chambers separated by a semipermeable membrane, one chamber of which has blood flowing through it while the other has a cleaning fluid—the dialysis fluid—flowing through it. For this purpose, commercial hemodialyzers usually have thousands of hollow fibers, the walls of which are semipermeable for the substances to be exchanged. Blood passes through the interior of the hollow fibers while dialysis fluid is fed into and removed from the fiber interspace, usually in the opposite direction.
Dialysis fluid contains blood constituents such as electrolytes in concentrations corresponding approximately to those of a healthy person, so that the corresponding concentrations in the blood can be kept at a normal level. Substances to be removed from the blood such as creatinine or urea are not present in the dialysis fluid, so they are removed from the blood by diffusion merely because of the concentration gradient on the membrane. With the help of a pressure gradient, excess water is withdrawn from the blood by convection and/or ultrafiltration.
To control such processes, hemodialysis machines are used to also ensure in most cases the preparation of the dialysis fluid from water and concentrates with the correct composition and temperature. In today's hemodiafiltration machines, this liquid is also used to compensate for the cleaning of blood (hemofiltration) brought about by increased convection. In hemodiafiltration, a larger amount of ultrafiltrate is withdrawn from the patient's blood during a hemodialysis treatment via the hemodialyzer and is replaced by replacement fluid up to the total amount of fluid to be withdrawn. With modern equipment, especially for treatment of chronic renal failure, the dialysis fluid prepared on-line during the treatment is used for this purpose by providing a line that branches off from the dialysis fluid circulation with one or more filter stages and by connecting it to the extracorporeal blood circulation upstream and/or downstream from the hemodialyzer.
The dialysis fluid itself is obtained from water and in most cases two concentrates which are mixed in a predetermined ratio by the hemodialysis machine. At the same time, the dialysis fluid is heated approximately to body temperature to perform the dialysis. The concentrates may be in liquid or dry form in smaller containers. In clinics and hospitals, the use of ring line systems with a central supply is also widespread.
The water and dialysis fluid must meet not only high requirements with regard to composition and temperature but also the microbiological purity is very important. To meet and ensure the required standards with regard to microbiological requirements (microbes, endotoxins), checking must be performed by sampling. Sampling is complicated because it is essential to prevent secondary contamination, which could falsify the microbiological tests.
To perform the sampling, so far additional components have been used. Sampling sites via self-closing septa, e.g., made of silicone, are widely used; these are installed in a line through which the flow passes. There are also T-shaped sampling sites for lengths of tubing that can be connected to a syringe without a needle. With all these approaches, it is essential that strict hygiene procedures be followed to prevent entrainment of secondary contamination through the sampling itself.
DE 103 36 539 A1 describes a T-shaped connecting piece for sampling fluids used in hemodialysis machines, in which the septum can be replaced easily. U.S. Pat. No. 5,630,935 describes a sampling valve for the water supply line of a hemodialysis machine.
DE 28 38 414 C2 describes a hemodialysis machine with which both fresh and spent dialysis fluid can be conveyed to a special sampling port with the help of the ultrafiltration pump. However, this requires additional lines and connections which must also be regularly included in the cleaning procedure.
The object of the invention is to improve upon a generic hemodialysis machine so that simple sampling of the prepared dialysis fluid is possible without any complex hygiene measures. The object of this invention is also to provide a corresponding method for sampling. Finally, another object of the invention is to provide simple sample containers for use with such a machine and such a method.